Continuous-wave terahertz imaging with a hybrid system

The authors have developed a hybrid system for coherent raster-scan imaging at $0.6\mathrm{THz}$ . It combines a high-power electronic source (a multiplied Gunn emitter) with a femtosecond Ti:sapphire laser in order to achieve a high dynamic range via electro-optic detection. The single-scan dynamic range of $60\mathrm{db}$ at a lock-in time constant of $10\mathrm{ms}$ is sufficient to permit detection of scattered terahertz radiation in addition to specularly reflected/transmitted light. Active synchronization of the electronic source and the laser is not needed because of the remarkably low jitter between the two radiation sources.